Hydrogeological study for improved nature restoration in dune ecosystems-Kleyne Vlakte case study, Belgium

In dune slacks a close coupling exists between changes in the hydrology and changes in species composition and vegetation structure. Consequently, there is a need to underpin nature restoration projects not only with ecologically relevant knowledge but also with scientifically sound hydrogeological data. In this paper, this necessity is illustrated through a study of the Flemish Nature Reserve 'The Zwindunes and Zwinpolders' (Belgian coastal plain) as an example. The management plan for the nature reserve suggests rewetting part of it to enhance its ecological value. The groundwater aspect was studied by means of field observations and mathematical modelling. First, fresh water head observation showed a mean groundwater flow from the nature reserve to the adjacent polder. Secondly, groundwater quality was studied with borehole measurements and water samples, resulting in a map of the fresh-salt water distribution and of water types. All available information was then put together in a density dependent groundwater flow model. The aim of this model was the description of current flow and fresh-salt water distribution and to simulate the impact of three possible rewetting scenarios. Rewetting will be accomplished by the infiltration of water in a depression, different lay-outs for which are considered. A zoomed in flow model based on a regional model was used to incorporate both local scale, which is of importance to ecology, and the larger scale, which determines general groundwater flow and fresh-salt water distribution. This modelling indicated differences between scenarios and was used to decide on the best rewetting strategy.